Coming dissertations at MedFak
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Cell-autonomous and paracrine mechanisms underlying Pik3ca-driven vascular malformations
Link: http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-521712
Vascular malformation is a benign overgrowth of blood or lymphatic vessels leading to life-threatening consequences for affected patients. Activating mutations in the TIE2 receptor cause the majority of venous malformations (VMs), while somatic activating mutations in PIK3CA, leading to the overactivation of the PI3K-AKT pathway, cause both VMs and lymphatic malformations (LMs). Although molecular inhibitors targeting the PI3K-AKT-mTOR pathway, such as rapamycin, have shown beneficial effects, they are not curative. This thesis aimed to explore the endothelial cell-autonomous and paracrine mechanisms underlying Pik3ca-driven pathological vascular growth to identify a rationale for improved and curative therapies for vascular malformations.
In Paper I, we reported that one of the most common causative mutations, PIK3CAH1047R, gives rise to two distinct LM subtypes known as macrocystic and microcystic LM in humans. Using a transgenic mouse model with temporally controlled LEC-specific activation of Pik3caH1047R, we found that the growth of microcystic LM is dependent on both the upstream pro-lymphangiogenic VEGF-C-VEGFR3 and the downstream AKT-mTOR signalling. Combination treatment targeting both signalling pathways led to effective inhibition of lesion growth in mice, suggesting a novel therapeutic approach for LM patients. In Paper II, we explored further the endothelial cell-autonomous and paracrine mechanisms underlying microcystic LM growth in mice. Using single-cell RNA sequencing, we identified a new immune-interacting subtype of dermal lymphatic capillary endothelial cells, termed iLECs. We showed that in Pik3ca mutant mice, iLECs produce factors that recruit pro-lymphangiogenic VEGF-C-producing macrophages. Macrophage depletion, inhibition of their recruitment, and anti-inflammatory COX-2 treatment resulted in decreased lymphatic growth, indicating a critical role of paracrine signalling between iLECs and immune cells in the pathogenesis of microcystic LM. In Paper III, we described distinct lymphatic vessel responses to oncogenic PI3K activation in different organs. We observed that while lymphatic vessels in the skin form microcystic LM through vessel sprouting, in certain other organs, they form large cysts reminiscent of macrocystic LM. Finally, we used mice with a BEC-specific activation of Pik3caH1047R to compare disease mechanisms in VM to those in LM in Paper II and to focus further on the former in Paper IV.
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Neuroimaging progesterone receptor modulation in patients with premenstrual dysphoric disorder : Is it just in your head?
Link: http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-521716
Premenstrual dysphoric disorder (PMDD) is a menstrually related mood disorder affecting about 5% of women during their reproductive years. The disorder is cyclic, with the symptomatology namely occurring at the luteal phase of a menstrual cycle, for most ovulatory menstrual cycles and entails a series of mood and physical symptoms. A neural susceptibility to regular hormonal fluctuations is hypothesized as the neuropathophysiological mechanism. While treatment options, such as selective serotonin reuptake inhibitors and hormonal interventions, are available, the neural mechanisms underlying symptom relief remain largely unclear. In this series of studies, a multimodal neuroimaging design was approach was used to reveal the neural correlates of three-month, low-dose selective progesterone receptor modulator (SPRM) treatment in comparison to a placebo. This treatment has been demonstrated to be effective in alleviating psychological symptoms associated with PMDD. Thirty-five women with fulfilling the criteria of a PMDD diagnosis were randomized to treatment with SPRM or placebo, with structural and functional MRI scans conducted before and after randomization. Findings indicated enhanced fronto-cingulate activity during a reactive aggression task in the SPRM treatment group compared to placebo, along with a negative association between aggressive responding and brain activity in the placebo group. Resting state functional connectivity was additionally altered after treatment with SPRM in fronto-visual, temporo-insular, and temporo-cerebellar regions. Additionally, a positive correlation was observed between the reduction in cortisol levels and the decrease in temporo-insular connectivity. No treatment effects were observed on brain structure, including grey and white matter volume, as well as cortical surface architecture. Lastly, White matter microstructure integrity did not differ longitudinally but showed cross-sectional differences. In conclusion, the effects of SPRM treatment were primarily observed in brain function, specifically in terms of enhanced cognitive control processing in the context of reactive aggression and resting state functional connectivity in regions relevant to cognitive and sensorimotor processing, with no significant structural alterations noted. Taken together, these findings confirm that the fluctuations rather than absolute levels of ovarian hormones are primary contributing to premenstrual symptomatology, potentially through hormonal-state dependent functional correlates.
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Physiological Studies of Native and Stem Cell-Derived Islets
Link: http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-520967
In type 1 and type 2 diabetes, the β-cells of the islets of Langerhans are either destroyed by the immune system or stressed due to peripheral insulin resistance. To improve the life of patients with these diseases, new treatments are needed. This thesis examined the role of irisin and cocaine and amphetamine regulated transcript (CART) in islets of Langerhans and their potential pharmaceutical role in type 2 diabetes. Furthermore, β-cell replacement with stem cell-derived islets of Langerhans (SC-islets) for type 1 diabetes was evaluated for optimal implantation site.
In paper I, the physiological role of CART in rat islets was examined. CART was shown to specifically lower islet blood flow, which could be a protective effect in type 2 diabetes. No effect from CART on glucose tolerance or insulin release was seen in rat islets, which highlights species differences.
In paper II, the expression of irisin and its effect on hormone secretion and pancreatic blood flow was examined. Irisin was expressed in human islets and was secreted glucose dependently. It also lowered islet blood flow but did not affect glucose-stimulated insulin secretion in isolated human or rat islets. Thus, local secretion of irisin could serve as a protective function by lowering islet blood flow in a high glucose state.
In paper III, the expression of irisin in SC-islets and its potential beneficial effects in transplantation was examined. SC-islets were found to express higher levels of irisin than human islets. Irisin treatment had no effects on viability and proliferation in SC-islets, in contrast to previous studies in other species. Thus, irisin signaling likely differs between SC-islets and murine and native human islets.
In paper IV, SC-islets were transplanted to multiple sites in mice to find the optimal implantation site in terms of graft maturity, function and composition. The liver proved to be the most favorable site due to its higher expression of islet maturity genes and a higher β-cell function and fraction. This poses a dilemma, as the liver site is the most challenging to biopsy and monitor for safety.
In summary, this thesis uncovered new physiological functions of irisin and CART, potentially offering insights relevant to the treatment of type 2 diabetes. Meanwhile, the role of irisin in transplantation of SC-islets seems limited.